Monolithic optical device for light transmission, and multi-channel optical system using same

ABSTRACT

An integrated light-transmission optical module for a safetyoptoelectronic barrier, comprises a condenser element having a first lens, and an objective having a second lens which are located respectively at a first end and a second end. The module comprises a single-piece entity made of transparent material, and having an intermediate zone provided with deflectors formed by a succession of dioptric surfaces distributed along the direction of light flux propagation between the first lens and the second lens. The deflectors ensure a deflection outside the optical module of stray rays reflected inside the module, so as to prevent transmission of strays rays, either through the second lens of the objective if it is a light transmission coming from the condenser element, or through the first lens when receiving light coming from the second lens.

BACKGROUND OF THE INVENTION

The invention relates to a light-transmitting optical device comprisinga condenser element equipped with a first lens to concentrate the lightin the opening of a second lens of an objective designed to emit orreceive an optical beam.

STATE OF THE ART

Light-transmitting optical devices generally use a system of lenses anddiaphragms arranged in an optical chamber. It is imperative to provide amechanical support designed to position the different parts with respectto one another with precision. Opto-electronic barriers generally havetwo hundred monitoring light beams requiring a total of four hundredlight-transmitting optical devices on the transmitter side and receiverside. The large number of mechanical supports increases the cost priceof the installation.

OBJECT OF THE INVENTION

A first object of the invention is to achieve a light-transmittingoptical device in one single part able to eliminate any stray light raysnot in the transmitting or receiving primary light beam passing throughthe objective. What is meant by primary light beam is all the light rayspassing directly from one lens to the other. Any light ray taking anon-direct path is defined as being a stray ray.

The device according to the invention is characterized in that:

the first lens of the condenser element and the second lens of theobjective are respectively arranged at one first end and at a secondopposite end of an integrated optical module made of a transparentmaterial having a predetermined refractive index,

the intermediate zone of said integrated optical module comprises aplurality of deflectors formed by a succession of dioptric surfacesarranged at intervals along the direction of propagation of the lightflux between the first lens and the second lens so as to performdeflection outside the optical module of the stray rays reflected insidethe optical module, thereby preventing transmission of said stray rayseither through the second lens of the objective if a light transmissioncoming from the condenser element is involved, or through the first lensif receiving light coming from the second lens.

The single-piece structure of the optical light transmission deviceavoids the use of an optical chamber equipped with mechanical supportand positioning parts. This results in a reduction of the overall costof the optical light transmission device.

According to a preferred embodiment, a diaphragm can be associated tothe first end of the integrated optical module and comprise a calibratedorifice to determine the angular opening of the useful optical beamemitted or received by the objective.

In the absence of a diaphragm, it is the size of the first lens thatdetermines the angular opening of the optical beam emitted or receivedby the objective.

The second lens of the objective presents a preset focal distance whosefocus is advantageously identical to the plane of the diaphragm.

In the absence of a diaphragm, the second lens constituting theobjective presents a preset focal distance whose focus is identical tothe opening plane of the first lens constituting the condenser.

The shape and positioning of the dioptric surfaces of the deflectors arechosen to ensure lateral ejection by refraction of the stray raysreflected in the integrated optical module.

According to one feature of the invention, the material of theintegrated optical module has a quality of transparency in the 360 nm to1560 nm pass-band.

According to another feature of the invention, the dioptric surfaces arealternately convergent and divergent being joined to one another bycoaxial necks presenting increasing diameters in the direction of theobjective so as to define with the diaphragm a primary optical coneinside the module.

A second object of the invention is to achieve a multichannel opticalsystem using a plurality of integrated optical modules, preventing anylight interference between the different channels.

An opto-electronic means is placed in each channel in front of the firstlens of the corresponding condenser element and is formed either by alight-emitting diode in transmitter mode or by a photodiode in receivermode. The different optical modules are integrated in parallel manner atregular intervals in a support plate equipped with salient fixing partsfor clipping onto an electronic circuit housed inside a hollow elongatesectional part. The different modules of an optical system are joined toone another, opposite from the plate, by rigid connecting bridges whosefront faces are cut into prisms and comprising in addition flexible tabsto act as pressure means when mechanical securing is performed insidethe sectional part. The second lens of each objective of the opticalmodules is housed in an opening of the sectional part so as to be ableto emit or receive the light beam.

Such a multichannel optical system can be used for constructingopto-electronic barriers equipped for protection of workers operating ondangerous machines.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages and features will become more clearly apparent from thefollowing description of an embodiment of the invention given as anon-restrictive example and illustrated in the accompanying drawings, inwhich:

FIG. 1 is a perspective view of a light-emitting optical deviceaccording to the invention;

FIG. 2 illustrates the path of the rays in the light-emitting opticaldevice according to FIG. 1;

FIG. 3 represents an axial sectional view of the optical device of FIG.1;

FIG. 4 is a perspective view of a multichannel optical system composedof several optical modules according to the invention;

FIG. 5 represents an axial sectional view of the optical system of FIG.4;

FIG. 6 is a cross-section along the line 6—6 of FIG. 5;

FIG. 7 shows a bottom view of the optical system of FIG. 4;

FIG. 8 represents the optical system integrated in an aluminium sectionto constitute an opto-electronic barrier;

FIG. 9 shows a perspective view of the opto-electronic barrier equippedwith a modular assembly of several optical systems according to theinvention.

DESCRIPTION OF A PREFERRED EMBODIMENT

With reference to FIGS. 1 to 3, a light-transmitting optical device 10comprises a condenser element 12 formed by a first lens 14 toconcentrate the light in the opening of an objective 16 equipped with asecond lens 18 designed to emit or receive an optical beam 20.

The first lens 14 of the condenser element 12 and the second lens 18 ofthe objective 16 are arranged respectively at one first end 22 and at asecond opposite end 24 of an integrated optical module 26 achieved by astraight single-piece entity made of transparent material having apredetermined refractive index and a quality of transparency in the 360nm to 1560 nm pass-band, i.e. in the visible and infrared field.

The intermediate zone 28 of the integrated optical module 26 comprises aplurality of deflectors 30A, 30B, 30C, 30D formed by a succession ofdioptric surfaces D1 to D7 symmetrically arranged at intervals along thelongitudinal direction of internal propagation of the light flux betweenthe first lens 14 and the second lens 18. The role of the dioptricsurfaces D1 to D7 consists in performing deflection of the stray raysreflected inside the optical module 26, thereby preventing transmissionof these stray rays either through the second lens 18 of the objective16 when transmission of light coming from the condenser element 12 isinvolved, or through the first lens 14 when receiving light coming fromthe second lens 18.

An opto-electronic means 32 is placed in front of the first lens 14 ofthe condenser element 12 with an interposed diaphragm 34 provided with acircular orifice 36 calibrated according to the angular opening of thesecond lens 18 that determines the diametric dimension of the usefuloptical beam 20 emitted or received by the objective 16. Theopto-electronic means 32 can be a light transmitting means or a lightreceiving means.

The second lens 18 of the objective 16 presents a predetermined focaldistance whose focus F1 is advantageously identical to the plane of thediaphragm 34.

In the case of a transmitter device, the opto-electronic means 32 isformed by a light-emitting diode LED or any other light sourceco-operating with the condenser element 12 to concentrate the usefullight rays RU into a primary conical beam directed onto the surface ofthe second lens 18 after it has passed longitudinally through thetransparent material of the module 26. The shape, number and positioningof the dioptric surfaces D1 to D7 of the deflectors 30A, 30B, 30C, 30Dare chosen to ensure lateral ejection by refraction of the stray rays RPreflected in the integrated optical module 26. Ejection by refraction ofthe stray rays RP can take place after at least one internal reflectionon one of the dioptric surfaces D1 to D7 depending on the value of theangle of incidence.

The dioptric surface D1 of the first deflector 30A presents a curvedshape, notably a logarithmic spiral shape, enabling total reflection ofmost of the stray rays outside the optical cone of the useful rays RU.All the other dioptric deflection surfaces are in the shape of taperedcones, either divergent for the surfaces D2, D4, D6 or convergent forthe surfaces D3, D5, D7 in the direction of propagation of the primarybeam towards the objective 16 when in transmitter mode.

The dioptric surface D1 is joined to the dioptric surface D2 of thesecond deflector 30B by a first neck C1 having a diameter of about 3.5°mm. The dioptric surface D3 is joined to the dioptric surface D4 of thethird deflector 30C by a second neck C2 having a diameter of about 4°mm. The dioptric surface D5 is joined to the dioptric surface D6 of thefourth deflector 30D by a third neck C3 having a diameter of 4.5° mm.The last dioptric surface D7 bounds at the end 24 the periphery of thesecond lens 18 of the objective 16 whose diameter is 6° mm.

The increasing variation of the diameters of the three coaxial necks C1,C2, C3 of the deflectors 30A to 30D in the direction of the objective 16enables the primary optical cone of the useful rays RU inside theintegrated optical module 26 to be defined with the diaphragm 34. Allthe other stray rays outside the optical cone are reflected on one ormore dioptric surfaces and ejected laterally to the outside afterrefraction (see rays RP).

In the case of a receiver device, the opto-electronic means 32 areformed by a photodiode.

FIGS. 4 to 7 represent a multichannel optical system 38 composed ofseveral optical modules 26 fitted in parallel at regular intervals on asupport plate 40 of rectangular shape. The support plate 40 is equippedwith fixing parts 42 extending perpendicularly to the flat surface ofthe plate 40 and salient from the first lens 14 of the condenser element12. Clipping and positioning pins 44 are arranged at one of the ends ofthe plate 40, whereas the other end comprises holes 46 of conjugateshape to those of the pins 44. The presence of the pins 44 and holes 46enables modular assembly of several optical systems 38 depending on thenumber of channels required.

Opposite the plate 40, the different modules 26 of an optical system 38are joined to one another by rigid connecting bridges 48 whose frontfaces are cut into prisms 50. Flexible tabs 52 also form an integralpart of the connecting bridges 48 to act as pressure means whenmechanical securing is performed in a piece of equipment.

The different modules 26 of an optical system 38 are achieved by plasticinjection or by any other forming process, in particular by pressure.The material used is a thermoplastic, in particular a transparentpolyacrylic such as methyl polymethacrylate PMMA. It is clear that othertransparent materials, in particular polycarbonate, glass, crystal, etc.can be used.

With reference to FIGS. 8 and 9, the optical system 38 is used toachieved safety or monitoring equipment, for example an opto-electronicbarrier for protection of workers operating on dangerous machines. Theopto-electronic barrier 54 comprises a hollow aluminium sectional part56 whose length depends on the zone to the monitored. An electroniccircuit 58 is inserted in a groove 60 inside the sectional part 56 andcomprises a multitude of light-emitting diodes LED or photodiodesdepending on whether it is a transmitting ramp or a receiving ramp thatis involved. A pierced intermediate plate covers the LEDs or photodiodesand acts as a diaphragm 34. The optical system 38 is then clipped ontothe electronic circuit 58 after the fixing parts 42 have been insertedin holes of the board. The second lens 18 of each objective 16 of theoptical modules 26 is housed in an opening 62 of the sectional part soas to be able to emit or receive the corresponding light beam 20. Theflexible tabs 52 exert pressure on internal bosses 64 of the sectionalpart 56 to perform mechanical securing of the optical system 38 on theelectronic circuit 58. FIG. 9 shows assembly of several optical systems38 extending longitudinally over a straight section of theopto-electronic barrier 54.

What is claimed is:
 1. A light-transmitting optical device, comprising:a condenser element having a first lens to concentrate light in anopening of an objective, the objective having a second curved lensdesigned to emit or receive an optical beam, wherein, the first lens ofthe condenser element and the second lens of the objective are arrangedat a first end and at a second opposite end, respectively of anintegrated optical module that is achieved by a straight single-pieceentity made of a transparent material having a pre-determined refractiveindex, and an intermediate zone of said integrated optical moduleincludes a plurality of deflectors formed by a succession of dioptricsurfaces which are arranged at intervals along the direction ofpropagation of the light flux between the first lens and the second lensso as to perform deflection outside the optical module of stray raysreflected inside the optical module, thereby preventing transmission ofsaid stray rays either through the second lens of the objective if alight transmission coming from the condenser element is involved, orthrough the first lens if receiving light coming from the second lens isinvolved.
 2. The light-transmitting optical device according to claim 1,wherein a diaphragm is associated to the first end of the integratedoptical module and includes a calibrated orifice according to an angularopening of a useful optical beam emitted or received by the objective.3. The light-transmitting optical device according to claim 1, wherein asize of the first lens is chosen according to an angular opening of theoptical beam emitted or received by the objective.
 4. Thelight-transmitting optical device according to claim 2, wherein thesecond lens of the objective presents a preset focal distance whosefocus is advantageously identical to a plane of the diaphragm.
 5. Thelight-transmitting optical device according to claim 3, wherein thesecond lens constituting the objective has a focus that is identical toan opening plane of the first lens.
 6. The light-transmitting opticaldevice according to claim 1, wherein the shape and positioning of thedioptric surfaces of the deflectors are chosen to ensure lateralejection by refraction of the stray rays reflected in the integratedoptical module.
 7. The light-transmitting optical device according toclaim 1, wherein the material of the integrated optical module has aquality of transparency in the 360 nm to 1560 nm pass-band.
 8. Thelight-transmitting optical device according to claim 6, wherein thedioptric surfaces are alternately convergent and divergent and joined toone another by coaxial necks that increases in diameters in thedirection of the objective so as to define with a diaphragm a primaryoptical cone inside the module.
 9. A multichannel optical system usingan integrated optical module according to claim 1 in each channel. 10.The multichannel optical system according to claim 9, wherein anopto-electronic means is placed in each channel in front of the firstlens of the corresponding condenser element and is formed either by anemitting means, in particular a light-emitting diode LED or a laserdiode, or by a receiving means, in particular a photodiode.
 11. Themultichannel optical system according to claim 9, wherein the differentoptical modules are integrated in parallel manner at regular intervalsin a support plate equipped with salient fixing parts for clipping ontoan electronic circuit that is housed inside a hollow elongate sectionalpart.
 12. The multichannel optical system according to claim 9, whereinthe different modules of an optical system are joined to one another,opposite from a plate, by rigid connecting bridges having flexible tabsto act as pressure means when mechanical securing is performed insidethe sectional part, and the second lens of each objective of the opticalmodules is housed in an opening of the sectional part so as to be ableto emit or receive the light beam.
 13. The multichannel optical systemaccording to claim 12, wherein the connecting bridges have front facescut into prisms to deflect the stray beams outside the primary lightcone.